Anthropologist george murdock sampled 565 societies and found that

George Murdock, an anthropologist, sampled 565 different societies and discovered that over 80% preferred some form of polygamy. Polygamy could steadily be found in at least five different countries during the majority of the 20th century. In Africa, it is believed that 20% of the men are involved in polygamous marriages. It was also discovered that 64% of societies around the world prefer one side of the family.

It could be anything, recent improvements in technology/telecommunication/internet have increased the pace of globalization.generally, it has something to do with technology. globalization means that people around the world are brought together through technology which speeds things up. so maybe some of those options could be correct. : )